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The main goal of the investigation was to measure and estimate the thermal stability of pinosylvin, pinosylvin monomethyl ether, robinetin, and dihydrorobinetin, i.e., characteristic compounds of wood of Scots pine and black locust, respectively. The pure compounds were analyzed with chromatography before and after they were steam-sterilized and oven-dried. Detailed thermogravimetric analysis was followed to check the thermal decomposition of the stilbenes and flavonoids of wood. The tested phenolic compounds were susceptible to thermal degradation. After the steam-sterilization and oven drying, the amount of investigated phenolic extractives decreased by more than a half. The thermogravimetric analysis showed that stilbenes decompose differently than flavonoids, which can be attributed to the different chemical structures. Twenty minutes of steam sterilization followed by 24 h of oven drying decreased the amount of phenolic compounds in the vials; however, after the applied thermal treatments, the stilbenes and robinetins stayed available in such quantities that they can still provide sufficient bioactivity. [ABSTRACT FROM AUTHOR]

The main goal of the study was to examine and compare the inhibition effect of knotwood extractives of Scots (Pinus sylvestris) and black pine (Pinus nigra) against the two white-rot fungi and two brown-rot fungi. Knotwood was extracted in a Soxhlet apparatus. Extracts were chemically analyzed, and the inhibitory effect of purified pinosylvins and crude hydrophilic extracts was tested against growth of the white-rot fungi Schizophyllum commune and Trametes versicolor and the brown-rot fungi Fibroporia vaillantii and Gloeophyllum trabeum with the in vitro antifungal assay. Knotwood of Scots pine and black pine contained comparable amounts of total extractives. Pinosylvin, pinosylvin monomethyl ether and nortrachelogenin were characteristic compounds in knotwood extracts of both pines. Scots pine knotwood contained larger amounts of pinosylvin than black pine. The ratio between pinosylvin monomethyl ether and pinosylvin was higher in black pine knotwood. Purified pinosylvins and crude hydrophilic extracts inhibited the growth of all the white-rot and brown-rot fungi tested. Pure pinosylvins better inhibited fungal growth than crude knotwood extracts, whereas the efficiency was not unambiguous and relates to fungi species. Crude hydrophilic extracts of Scots pine more efficiently inhibited fungal growth than extracts of black pine. With the present investigation, hydrophilic extracts of pine knotwood were demonstrated as formulations of natural compounds with good antifungal properties. Broken tops of Scots pine, which can lie on forest grounds for a month or even more, still contain high amounts of phenolic extractives and are therefore a potential raw material for recovery of bioactive compounds. [ABSTRACT FROM AUTHOR]

The extraction conditions have been evaluated concerning the recovery of specific polyphenols from Scots pine (Pinus sylvestris) knots by means of an accelerated solvent extractor. The composition of the extracts was determined by gas chromatography, gas chromatographymass spectrometry, and high-performance size-exclusion chromatography. The main phenolic compounds are the stilbenes pinosylvin and its monomethyl ether and the lignan nortrachelogenin (NTG), and their amounts vary a lot from sample to sample. The sequential extraction with a nonpolar solvent as a first step for removing the lipophilic compounds was the most efficient approach for the recovery of both pinosylvins and NTG. For food applications, hot water and 85% aqueous ethanol were good solvents for the production of the substances in focus. An industrial knotwood sample from a pulp mill was sequentially extracted with cyclohexane and ethanol/water (95:5) in a large-scale Soxhlet equipment. The results show that the industrial production of pinosylvins and NTG from knots is feasible. [ABSTRACT FROM AUTHOR]